Joseph Fiennes was a good 15 minutes late, and worse, couldn't be found by the frantic RSC press officer. I wasn't his only forgotten appointment, he confessed, when he did eventually appear, complete with fulsome apologies - but one look into his huge liquid brown eyes, surrounded by extraordinarily long eyelashes - and, ladies, you'd forgive this personable young man anything.

Brother to Ralph, who made an international name for himself with his portrayal of the brutal Nazi officer in Steven Spielberg's Schindler's List, Joseph is also making a name for himself within the profession - and quite probably among the female members of his audience too. It was, in fact, hard to equate this seemingly reserved and quietly spoken 25-year-old actor with the loud and lusty young character who'd been charging all over the stage of the main theatre in fine comic form in As You Like It. However, we'd actually met to talk about his creation of the role Rafe Smith in the new Peter Whelan play The Herbal Bed which opened for previews at The Other Place in Stratford last week.

The play is based on actual events 400 years ago when Shakespeare's elder daughter Susanna, wife of Stratford physician John Hall, was publicly accused of having a fling with a married neighbour Rafe Smith. On July 15, 1613, she sued for slander in the court of Worcester Cathedral.

Joseph elaborates: "A young boy, Jack Lane, of Alveston Manor, was taken on by John Hall as an apprentice and he's just a bit of a reckless young lad. "It's documented that he slandered Mistress Hall and said Rafe Smith, a local haberdasher who we know was a friend of the Halls, and the words are 'was naught' - naughty - with Rafe Smith.

"It was taken to the court but Jack Lane didn't appear - he also slandered the clergymen of Stratford and was a bit of a drinker and a loudmouth." Lane's non-appearance meant the case fell apart but, 400 years on, the barest details of those events are enough to create a play ripe with dramatic possibilities. Joseph says the play is more than a straightforward 'did they or didn't they' thriller. He says: "Nobody wins or loses and there's no right or wrong. Everybody is opened up to their vulnerable side and it exposes the vulnerability especially of the marriage between Susannah and John."

Obviously, no one knows the real truth but Joseph says the play sees Susannah and Rafe 'going all the way' only emotionally, but far enough for it to be a sin in the eyes of the church and his character. He explains: He's a man who's in turmoil. He idolises John Hall but he also practises his view of his puritan religion and he's caught up in doing what's right in John's eyes and in the eyes of the Bishop. Susannah is a woman 400 years ahead of her time and is very liberal-minded and he's very attracted to that. He puts her up on a pedestal but suddenly she turns round and says 'actually I think I might need you because my marriage is on the rocks.' It's a wonderful play but slowly their masks begin to fall."

It's certainly a play about interacting relationships rather than events, he states, pointing out to the potential audience member, though, that the whole evening is conducted on a knife edge. "Rafe is incredibly nervous in the cathedral under the eyes of God and you feel that he would blurt out at any moment that he was naughty with Mistress Hall."

One of the advantages of opening the play in Stratford has mean Joseph has been able to visit the same locations where certain things did (or didn't) happen.

"We went to Worcester Cathedral, which was fascinating," he says. Going to the Stratford locations also gave him a bit of a buzz. He says: "It definitely has a vitality and a feeling - once you've dodged the hundreds of tourists and tea rooms and you can finally get a quiet place." Joseph adds: "Hall's Croft is wonderful; I sat on the wall at midnight looking in - as Rafe does in the play."

While the play may focus on the lives of members of the Shakespeare family centuries ago, Joseph is at pains to point out that it is more than a story based in Stratford at a fixed point in time.

"It's about you, me and everyone in the audience who are married and who might have problems like this. "It's opened itself right out. I think that's how any great writing should be. You can do anything with it, manipulate it and it's still universal."